Method of manufacturing a reciprocal four-way spool valve



Sept. 21, 1965 METHOD OF MANUFACTURING A RECIPROGAL FOUR-WAY SPOOL VALVEOriginal Filed Nov. 7, 1958 3 Sheets-Sheet 1 Q k s:

% [EVEN/UP STA/VLDH/Jfll/MATS s. H. HOLMES 3,206,837

Sept. 21, 1965 s. H. HOLMES 3,205,837

METHOD OF MANUFACTURING A RECIPROCAL FOUR Original Filed Nov. 7, 1958WAY SPOOL VALVE 3 Sheets-Sheet 2 f w 2 4/ x i g p 21, 1965 s. H. HOLMES3,206,837

METHOD OF MANUFACTURING A RECIPROGAL FOUR-WAY SPOOL VALVE Original FiledNov. 7, 1958 3 Sheets-Sheet 3 fiYVEZY/UP JTA/VLD A/ HOLMES United StatesPatent 3,206,837 METHOD OF MANUFACTURING A RECIIROCAL FUUR-WAY SIGOLVALVE Stanley H. Hoimes, 4121 N. Springfield Ave, Chicago, Ill.Continuation of application Ser. No. 772,461, Nov. 7, H58. Thisapplication Dec. 11, 1961, Ser. No. 161,330 3 Claims. (Cl. 29-4571) Thisapplication is a continuation of my copending application Serial No.772,461 filed Nov. 7, 1958 entitled Method of Manufacturing a ReciprocalFour-Way Spool Valve, now abandoned.

The present invention relates to an improved relatively inexpensive,hydraulically actuated spacing table for drill presses, millingmachines, or like apparatus in which a workpiece is to be exactlypositioned relative to a tool and wherein the location of the workpiecerelative to the base or bed of the particular machine must be extremelyaccurate and capable of accurate repetition. The invention also relatesto a novel control valve for such a spacing table and other uses.

I-lydraulically actuated machinery has, of course, long been known inthe mechanical arts. It has many well recognized advantages overelectrical or mechanical drive systems both in cost and versatility.However, to my knowledge, hydraulic actuation has not been provided forsuch accuracy-requiring machinery as spacing tables for drill presses,drilling machines and similar equipment. This has been due to the factthat in the past sufficient accuracy of repetition has been unavailablein hydraulic systems at a cost low enough to make such systemscompetitively practical. The present invention, on the other hand, hasprovided a hydraulic spacing table apparatus which is not only extremelyaccurate but which is relatively inexpensive to manufacture in spite ofthe utilization therein of machining tolerances heretofore consideredimpractical, if not impossible of achievement.

In accordance with the principles of the present invention a hydraulicvalve of simple construction is provided in which a continuous flow ofhydraulic fluid is provided in a neutral position. Any deviation of thevalve from its neutral position causes a hydraulic flow in one directionor the other of a controlled part, in the present case a spacing tableor the like. By providing a valve of substantially perfect accuracy, itwill center itself consistently in the same position within onethousandth of an inch, or less. As a result, by securing one of the tworelatively movable parts of the valve to the spacing table and the otherpart to a relatively fixed part of the machine, the spacing table mayautomatically be exactly positioned by adjustment of the valve.

In further accordance with the present invention a master cam isprovided in associated relationship with the valve to provide a seriesof predetermined stop position points for the spacing table, such thatthe table may be stopped at a plurality of predetermined, relatedpositions. By providing a master cam for each series of operations it ispossible to provide sequential positioning of the spacing table for aplurality of work operations at essentially exactly positioned locationsrelative to the movable spacing table. As a result a large number ofworkpieces may be machined or otherwise processed in exact conformitywith each other by means of a simple, hydraulic system.

It is, accordingly, an object of the present invention to provide animproved and simplified hydraulic actuating system.

Still a further object of the present invention is to provide anextremely inexpensive servo control valve of extremely close tolerances.

A feature of the invention resides in a novel valve construction whereina four-way valve is constructed by machining alternate housing and valvecore parts simultaneously to provide essentially exactly the samedimensrons.

Still other and further objects and features of the present inventionwill at once become apparent to those skilled in the art from aconsideration of the attached drawings wherein preferred forms of theinvention are shown by way of illustration only; and wherein:

FIGURE 1 is an isometric view of a machinery spacing table incorporatingthe principles of the present invention;

FIGURE 2 is an enlarged detailed view in side elevation of a portion ofthe spacing table shown in FIGURE 1;

FIGURE 3 is a side elevational view of a portion of the control systemof the present invention;

FIGURE 4 is a cross-sectional view of the control valve incorporated inthe present invention, with related hydraulic parts diagrammaticallyshown; and

FIGURE 5 is an isometric view of a modified form of hydraulicallyactuated machinery table constructed in accordance with the presentinvention.

As shown on the drawings:

As may be seen from a consideration of FIGURE 1, the present inventioncomprises a movable work supporting table for machinery or the like.While the machine proper is not illustrated, it may comprise anyconventional milling machine, drill jig borer, drill press, or similarequipment of which a table is movable in a general horizontal plane, itwill be clear that the arrangement illustrated comprises a generallyfixed platform or base table 10 rigidly secured to the machine baseproper. A pair of spacer tables 11 and 12 are mounted relative to thetable 10 for horizontal movement on guideways 13 and 14 respectively.Such horizontal movement is achieved by means of a pair of hydraulicmotors 15 positioned between the movable table 11 and the base 10, onthe one hand, and by the hydraulic motors 16 interposed between themovable table 112 and the table 11. The motors 15 and 16 comprisegenerally conventional reciprocating piston and cylinder type hydraulicmotors or actuators. In each case the stroke of the piston relative tothe cylindrical housing in which it slides, slightly exceeds the designpath of movement of the respective movable table relative to the tableor base carrying it. As a result of this arrangement, energization ofthe respective fluid motors by a control valve will permit movement ofthe uppermost table 12, upon which a workpiece or the like is secured,into any position within the limits of horizontal travel of either thetable 11 or the table 12.

It will be apparent to those skilled in the art that the problem facedin providing a satisfactory work carrying table 12, positioned by meansof hydraulic motors lies mainly in providing sufficiently accuratecontrol to permit exact placement of the table. An approximate placementof the table is worthless for modern day machining operations.Substantially exact placement is, however, achieved in the cast of thepresent invention through utilization of the reciprocal power motors 15and 16 under the control of identical servo valves 17 and 18. Thespecific internal construction of the valves 17 and 18 may be moreclearly understood from a consideration of FIGURES 2-4.

In FIGURE 4 the valve 17 is specifically illustrated. It will beunderstood, however, that the valve 18 is identical in constructiontherewith. As there shown, the valve comprises a fixed housing 21rigidly secured to the base table member 10. The housing 21 comprisesend plates 22 and 23 secured to a generally cylindrical portion 24 bymeans of cap screws 25, or the like. Within the bore 24:: of the housingmember 24, the plurality of annular segments 26, 27, 28, 29, 30, 31 and32 are provided. As will be apparent from a consideration of thedrawings, the outside diameter of each of these segments or diskscorresponds substantially with the internal diameter of the bore 24a.Accordingly, upon assembly of the respective segments within the bore24a, and securement of the covers 21 and 23 to the portion 24, a rigidassembly is provided. Within the generally longitudinal bore providedwithin the annular segments or disk members 26, 27, 28, 29, 30, 31 and32, a valve core generally indicated at 34 is provided. The corecomprises a spool 35 carrying annular segments 36, 37, 38, 39, 40, 41and a rigid abutment member 42. The respective segments 36, 37, 38, 39,40 and 41 are rigidly maintained in position by means of a threadedconnection comprising threads 43 on the core portion 35 and internalthreads 44 in the annular segment 36. The core 34 is centered relativeto the longitudinal axis of the bore 24:: in a manner described belowand is sealed relative to the housing by a pair of flexible diaphragmseals 45 and 46 which are clamped, respectively, between the disks 26,27 and 36, 37 at the left-hand end as viewed in FIGURE 4 and between thedisks 31, 32 and 41, 42 at the right-hand end of the valve as viewed inFIGURE 4. These diaphragms are constructed of any convenient resilientmaterial such as flexible metal, plastic, reinforced rubber or the likeand operate to maintain the valve core 34 axially centered relative tothe bore 24a while permitting its longitudinal reciprocation relativethereto. This reciprocation may be accomplished externally in a mannerto be described below and is limited, in the form of the inventionillustrated, to a small fraction of an inch total relative travel. Thislimitation is imposed by the fact that the disks 38 and 40 are of largerdiameter than the enclosing disks 27, 29 and 31 and accordingly abut thelatter disks upon reciprocal movement away from a centered condition.Such abutment, in the direction of left-handed core movement as viewedin FIGURE 4, is illustrated in that figure with the disks 3S and 41) incontact with the respective disks 27 and 23.

As may be seen from FIGURE 4, the disks 2? 29 and 30 are providedrespectively with annular hydraulic passageways 28a, 29a and 30a whichare connected, repectively, to ports 29b, 30b and 31b in the housingportion 24. The ports 2%, 30b and 31b connect, respectively, with afirst side of the hydraulic motor 15, as at 1.5a, a source of fluidunder pressure 49, and a second side of the fluid motor 15, as at b. Therespective disks 27 and 31 are likewise provided with annular grooves26a and 31a which are connected to a common sump port 50 leading to alow pressure reservoir 51 of the pump 49.

The core 34 of the valve is normally positioned relative to the housing24 by means of a pair of helical springs 52 and 53 shown, respectively,in FIGURES 4 and 2. As shown, the spring 52 is supported by an abutment52a and acts directly against the left-hand end of the core 35. At theother end, however, the spring 53 is supported by an abutment 53acarried by the fixed base table 10 and acts against bracket 54 pivotallymounted on the frame 10 at pin 55. The bracket 54 carries a centeringball 56 which co-operates with the centering hole 57 in a cam abutmentbar 58. The cam abutment bar has a centering hole 59 at its left-handend as viewed in FIGURE 2 which, in turn, co-operates with a centeringball 60 carried by a bracket 61 pivotally mounted on a pin 62. Thebracket 61 rests against the rounded end of threaded extension 63adjustably secured relative to the core 34 by means of a lock nut 64.Adjustment of the respective screws 52b and 53b permits accurateadjustment of the spring forces acting on valve core 34. In the eventthat a cam abutment bar 58 having slightly different lengths isemployed, the further adjustment at 64 may be utilized if desired.

In the centered position of the valve core 34 it will be clear thatfluids pumped from the pump 49 through port b will divide and flowequally into the annular recesses 38a and 40a, and from thence to sump51, thereby applying identical pressures to the sides 15a and 15b of theactuating motor 15. It is preferable that the output of the pump 49 begreater than the maximum flow rate passed by the valve 17 when in itsneutral or open position. As a result of such an arrangement, a positivepressure will exist in both chambers 38a and 40a when the valve is inneutral, and this oil under pressure will resist any movement of thetable by externally applied forces. However, upon shifting of the coreinto a position away from centered, such as for example in the left-handposition as shown in FIGURE 4, fluid pressure applied to the annularchamber 39a will be applied to the chamber 38a and chamber 15a of thefluid motor 15 at an increased rate. Simultaneously, contact between thechamber 3% and chamber 40a will be cut off by the annular segment 40.Also, simultaneously, the chamber 40a will be more fully ported to thesump chamber 41a and the sump chamber 37a will be disconnected from theannular chamber 38a by the left-hand face of the segment 38. In thecircumstances, positive pressure is applied to side 15a of the motorwhile the pressure applied to the side 15b drops to sump pressure, withresultant right-hand movement of the piston 15c relative to the motorcylinder 15. Preferably motor 15 is secured to fixed attachment brackets15c rigidly attached to the base table 10. Accordingly, pressurizationof chamber 15a and depressurization of chamber 15b upon left-handmovement of the valve core 34 causes right-hand movement of the table 11while, conversely, pressurization of chamber 15b and depressurization ofchamber 15a upon right-hand movement of core 34, causes a left-handmovement of the table 11.

In operation, the valve core 34 is centered relative to predeterminedreference points determined by the cam abutment bar 58. It will be seenfrom a consideration of FIGURES 1 and 2 that the table 11 carries,secured thereto, an indicator box 71 Adjustably mounted relative to thebox is a bracket 71 carrying a dog '72 pivotally mounted on a pin 73.The dog 72 is gravitationally biased downward, or in the clockwisedirection into an interference relation with abutment 58a of the camabutment bar 58. With the dog in the position shown, therefore,right-hand movement of the table 11, carrying the dog toward the right,will cause movement of the cam abutment bar 58 toward the rightcompressing spring 53 and permitting spring 52 to move the valve core 34toward the right which in turn will cause energization of the motor 15to cause movement of the table 10 and the dog 72 toward the left tocenter the valve. At the point in which the spring 53, which is strongerthan 52, is effectively counterbalanced by the force applied by dog 72and spring 52, the table will come to a centered, rest, condition, whichposition will be exactly controlled by the position of the abutment 58aand the cam abutment bar 58. The table 16 may be moved to a furtherright-hand position by lifting the dog 72. Such lifting movement willpermit the spring 53 to override the spring 52 causing movement of thetable 10 toward the right until it strikes a second cam abutment 58bwhen the above-mentioned centering action will again take place.Disengagement of the dog 72 from the abutment 58a, 58b with which it isin contact may be accomplished by counterclockwise movement of thehandle 75. Such movement causes a cam surface 76 to engage delatchingbar 77, shown in FIGURE 3. The bar 77 is slotted as at 78, 78 and ismounted on pins 79, 79 carried on the base table 10. Accordingly,movement of the bar 77 toward the right by the cam surface 76 will causever tically upward movement of the bar 77, which vertically upwardmovement engages the dog 72 pivoting it momentarily out of contact witha respective cam abutment and permitting movement of the table 11 towardthe right. Maintenance of the handle in its delatching position willpermit movement of the table toward the right past such of the camabutments as the operator may desire to pass and centering of themachine into an adjusted table position will not take place until thelever 75 is returned to its neutral position and the dog 72 is permittedto engage one of the abutments. Movement of the table 11 in theleft-hand direction may readily be accomplished by rotation of thehandle 75 in the clockwise direction in which event the cam projection78 engages the bracket 61 biasing it in the clockwise direction andrelieving the pressure of the spring 53 from the valve core 34 causingthe core 34 to move toward the right-hand side under the influence ofspring 52. As explained above, this right-hand movement of the valvecore 34 will cause left-hand movement of the table 11 until such time asthe handle 75 is returned to its neutral, vertical position as shown inFIGURE 2.

In the specific form illustrated in FIGURES 1 and 2, the cam abutmentbar 58 is provided with abutments 58a, 58b, etc., spaced equally oneinch apart. With such an arrangement the table may be positioned exactlyat one inch increments by counterclockwise manipulation of the handle 75and release thereof as soon as the dog 72 has cleared each successiveabutment. The position of the table is indicated on a dial 80 driventhrough a spring clutch 81 rotated by worm gear 82. The worm gear 82 isin turn driven by a helical gear 83 in spur gear engagement with therack 84. The rack 84 is, as shown in FIG- URE 1, rigidly secured to thebase table It), and accordingly, as the indicator box 70 moves with thetable 11, the rack 84 rotates the helical gear 84 to operate the dial80. An initial adjustment of the indicator 80 may readily be provided bymanually setting the indicator 80 relative to the clutch 81 which ismerely a friction drive connection.

The indicator box 70 is also provided for means for providing an exactpositioning of the table intermediate the one inch incrementsestablished by the cam abutment bar 58. This is accomplished by movementof the dog 72 relative to the table 11. In the form illustrated, suchmovement is accomplished by means of a manual crank 85 operativelydriving a rotatable screw 86 threadably engaged with the dog carryingblock member 71. The block member 71 may be moved throughout a range oftwo inches. This posit-ion is exactly indicated on indicator 87 operablethrough a one inch range by reciprocal push rod 88. The indicator 87 maybe of any conventional form and may be accurate to 4 of an inch.Obviously, if the table is moved to a position in which the dog abutsagainst the abutment 58a, the table 11 may be moved a distance less thanan additional inch by adjusting the block 71 toward the left. Thedistance of such movement is exactly indicated on the indicator 87 and,as the block 71 moves toward the left the table is permitted to movetoward the right until dog 72 acts against the abutment 58a to balancethe valve 17. As a result of this arrangement the position of the table11 may be exactly spaced in an extremely simple manner. Provision of atwo inch range of movement for block 71 allows initial set up adjustmentwithin that range.

It will, of course, be apparent that the positioning or spacing of thetable 12 may be accomplished in exactly the same manner as table 11except that table 12 uses as its fixed point of reference the table 11and travels in a direction transversely of the path of movement of table11. Exactly the same control equipment may be used, as indicated inFIGURE 1 where the indicator box and valve are illustrated and carry thesame numbers employed in the description above.

A zero adjustment for the indicator 87 is provided by an adjusting screw89 passing through the block 71 and abutting against the right-hand endof the reciprocal plunger 88. Through the use of this adjusting screwany base reference point may be employed in spacing of the apparatus,which reference point may be determined by the actual position of thework when bolted to the table 12.

Satisfactory operation of a hydraulic table of the type hereinabove setforth requires, when it is to be employed in manufacture of parts havingcritical dimensions, that the valve 17 be absolutely accurate. This isaccomplished in an extremely simple manner in accordance with theprinciples of the present invention. As above indicated the valve isconstructed of a plurality of stacked disk members. To provide exactlyaccurate operation it is essential in such a reciprocating valvestructure that the disk 38 and the disk 40 contact the respective disks27 and 29 simultaneously when the valve core is moved to the left and,conversely, contact the respective disks 29 and 31 when the valve coreis moved to the right. If one disk contacts while the other is out ofcontact inaccuracy of control results. This is true whether or not thedisks 38 and 40 are larger in diameter than the internal diameter of theannular disk members 27, 29 and 31. If the disks 38 and 40 are, forexample, the same diameter as the internal diameter of the disks 27, 29and 31 the minimum flow cut-off point is still determined by the pointat which the outer peripheral edge of the disks 38 and 4t)instantaneously overlap the respective disks 27, 2?, or 29 and 31.

In the manufacture of valves heretofore known, the exact dimensioning ofthe respective disks has been a major problem and to provide such exactdimensions has been extremely costly. As those skilled in the art ofmachinery are aware, manufacture of any parts having a large number ofsurfaces which must bear a relationship to each other within or less, isextremely expensive and is, in many instances, practically impossible ofaccomplishment on a mass production scale at all. In the presentstructure, however, its accomplishment is both simple and inexpensiveand, further, readily adapted to mass production techniques. Inmanufacturing the core and housing assembly, the disks 38, 29 and 40 aremachined to the same axial thickness. The disks 28, 39 and 30 are allmachined to a second, larger, thickness. It is relatively unimportantwhat the difference between these two thicknesses is, except insofar asit dictates the dimensions of the maximum flow orifice (as for examplebetween the disk 38 and the disk 29 in FIGURE 4). The sameness of axialdimension of the three disks 38, 29 and 40 may be accomplished byplacing all three disks on a flat grinding machine table and passing allthree under a grinding wheel. If desired, the three may be lappedsimultaneously on a lapping table subsequent to the grinding operation.By grinding and lapping the three disks simultaneously on the same tablethey will all have the same thickness substantially exactly even thoughthere may be a slight variation between sets of disks. Similarly, thethree disks 28, 39 and 30 are simultaneously ground and lapped on thesame machine table. The result of this method of manufacture is a valvein which the disks 38 and 4t! will bear exactly the same relationship tothe respective disks 27, 39 and 31, and accordingly, the valve will beperfectly balanced. The annular grooves 38b and 40b are provided toprevent hydraulic forces acting against the disks 38 and 40 from actionto retain the valve in an uncentered position and assure hydraulicbalance of the valve core.

It will be apparent to those skilled in the machinery arts that byemploying the above method of operation phenomenal tolerances areachieved. These tolerances are achieved in the simplest of manners andwithout the need of extremely accurate and complex equipment employed inprior art methods. It has been found that valve manufactured inaccordance with this method provide, in operating a spacing table,substantially exact table placement time after time, duplicating theperformance of equipment many times the cost of the relatively simplehydraulic apparatus herein described.

The valve of the present invention, as above described may also beemployed in providing a variable speed drive of a hydraulic type, for amovable table. This is illustrated in FIGURE 5. As there shown, a basetable 110 carries a constant pitch lead screw 111 mechanically driven byany desired form of variable speed drive, indicated at 112. This maycomprise a light duty gear drive mechanism having an output torque onlymoderately in excess of the torque required to rotate the screw 110,since for the reasons to be advanced below, the drive screw pro videsnone of the actual power for operation of the spacing table 113. Thetable 113 is hydraulically driven by means of conventional reciprocatingtype piston and cylinder hydraulic motor 114 having a piston rod 115.The piston rod 115 is secured in any conventional manner to the table113 and the cylinder 114 is likewise secured in any conventional mannerto the base table 110. A hydraulic servo valve 17, constructed the sameas valve 17 shown in FIGURES l4, is secured to the table 110. The corethereof, not specifically illustrated in FIGURE 5, is centeredinternally by axially operating springs, not shown, in the same manneras spring 52 is applied in FIGURE 4. The core 170 has secured thereto avertically upstanding arm 171 engaged with an annular groove 172 in thelead screw 111. The lead screw 111 engages a half nut 173 rigidlysecured to the table 113 at support 113a. Hydraulic movement of thetable 113 is then readily accomplished by starting the variable speeddrive, such as by energization of an electric motor thereof. Rotation ofthe lead screw 111 will, assuming the table 113 is initially immovable,cause reciprocation of the lead screw 111 against the arm 171 and thecentering springs of the valve 17. This reciprocation will uncenter thevalve 17 and cause actuation of the motor 114 to move the table 113.Since the table 113 carries the half nut 173 with it the movement of thetable 113 will continue at a rate exactly controlled by the rate ofrotation of the lead screw 111. If the table were to lag behind, thevalve 171 would be reciprocated to a further open position while,alternatively, if the table were to advance faster than the rate of thescrew 111 dictated, the valve 17 would be centered and no additionalmotor power would be applied to the motor 114. Obviously, the onlylimitation on the rate of movement of the table 113 is the maximum rateof flow permitted by the valve 17 and this rate may readily becontrolled by the difference in thickness between the respective sets ofvalve disks containing the disks 28, 39, 3t and 38, 29, 40 as above setforth. The table may also be advanced manually by providing an extension111a of the lead screw 111. The extension 111a is provided with a squareend 111b to which a wrench handle may be attached. In the above manner,an extremely heavy table 113 may be moved by a device having practicallyno torque output requirement or, manually, with a minimum of effort.Further, although the table 113 is moved by hydraulic power, the rate ofmovement is exactly controlled and is dependent only on the accuracy ofthe small, and relatively delicate, variable speed drive which,accordingly, may be constructed with extreme accuracy.

It will be apparent to those skilled in the art that the output of pump49 may be varied, if desired, by any conventional means, to providedifferent neutral pressures in the motor 15. Further, it will be seenthat the abutment cam bar 58 may comprise a threaded bar having aplurality of nut abutment members threaded thereon so that the abutmentsmay easily be adjusted relative to each other to provide a sequence ofspacings for a mass production job in which many parts are to be madeemploying the same spacing sequence. The bar 58 may, if desired, berotated on its axis by an indexing means between successive tablepasses. For example, the abutments 58a, 58b, etc., may have an angularwidth approximately 60 and rotation of the bar 58 60 after the firstpass of the table would permit a second series of abutments unrelated tothe first series, to control the next pass of the table. Thus six cambars could be combined into a single bar unit. A convenient indexingmechanism would comprise, for example, a spring detent ball on thesurface of the member 54 facing the bar 58 and'adapted to seat in one ofsix angularly spaced sockets in the end face of the cam bar depending onthe angular position of the bar 58.

It will be clear from the above description that I have provided agreatly improved hydraulic table moving apparatus and valve mechanismtherefor. Since variations and modificatons beyond those above discussedmay obviously be readily accomplished without departing from the scopeof the novel concepts of the present invention, it is my intention thatthe scope of the present invention be limited solely by the scope of thehereinafter appended claims.

I claim as my invention:

1. The method of manufacturing a reciprocal fourway spool valve having areciprocal core comprising a pair of annular land portions spaced by anannular reduced diameter portion and a housing co-operable therewithcomprising a pair of annular portions of large internal diameter spacedby a first annular portion of re duced internal diameter and which inturn space a second pair of reduced diameter portions, which consists offorming each of said portions as a separate annular member and machiningsaid pair of annular land portions and said first annular portion ofreduced internal diameter simultaneously to the same thickness andlikewise machining said pair of annular portions of large internaldiameter and the annular reduced diameter portion of said coresimultaneously to a second same thickness and assembling said core andhousing together with the annular lands of the core in face-to-facecorrelation with the housing portions of large internal diameter andwith the reduced diameter portion of the core in face-to-face relationwith the first reduced internal diameter portion of the housing and withthe second pair of reduced diameter portions positioned on axiallyopposite sides of said annular portions of large internal diameter.

2. The method of manufacturing a reciprocal fourway spool valve having areciprocal core comprising a pair of annular land portions spaced by anannular reduced diameter portion and a housing co-operable therewithcomprising a pair of annular portions of large internal diameter spacedby a first annular portion of reduced internal diameter and which inturn space a second pair of reduced diameter portions, which consists offorming each of said portions as a separate annular member and machiningsaid pair of annular land portions and said first annular portion ofreduced internal diameter simultaneously to the same thickness andlikewise machining said pair of annular portions of large internaldiameter and the annular reduced diameter portion of said coresimultaneously to a second same thickness, and wherein said simultaneousforming is accomplished by placing the respective parts simultaneouslyon a grinder bed plate on their axially facing side surfaces and surfacegrinding the axial surfaces thereof together by the same grinding wheeland assembling said core and housing together with the annular lands ofthe core in face-to-face correlation with the housing portions of largeinternal diameter and with the reduced diameter portion of the core inface-to-face relation with the first reduced internal diameter portionof the housing and with the second pair of reduced diameter portionspositioned on axially opposite sides of said annular portions of largeinternal diameter.

3. The method of manufacturing a reciprocal four-way spool valve havinga reciprocal core comprising a pair of annular land portions spaced byan annular reduced diameter portion and a housing co-operable therewithcomprising a pair of annular portions of large internal diameter spacedby a first annular portion of reduced internal diameter and which inturn space a second pair of reduced diameter portions, which consists offorming each of said portions as a separate annular member and-l'1'lE1Chln-.

ing said pair of annular land portions and said first annular portion ofreduced internal diameter simultaneously to the same thickness andlikewise machining said pair of annular portions of large internaldiameter and the annular reduced diameter portion of said coresimultaneously to a second same thickness, and wherein the simultaneousmachining comprises the step of placing the respective partssimultaneously on a flat surface on their axially facing surfaces andremoving metal from the 0pposite axially facing surface by a toolpassing over the respective parts sequentially without change ofadjustment relative to said plate and assembling said core and housingtogether with the annular lands of the core in face-toface correlationwith the housing portions of large internal diameter and with thereduced diameter portion of the core in face-to-face relation with thefirst reduced internal diameter portion of the housing and with thesecond pair of reduced diameter portions positioned on axially oppo- 10site sides of said annular portions of large internal diameter.

References Cited by the Examiner UNITED STATES PATENTS 2,051,052 8/36Morgan 90-21.5 2,559,839 7/51 Andrew et a1. 90-215 2,705,829 4/55 Mock29157.1 2,796,081 6/57 Dannevig et a1. 29157.1 X 2,839,079 6/58 Holmes137-6255 X 3,052,963 9/62 Williams 29157.1

WHITMORE A. WILTZ, Primary Examiner.

RICHARD H. EANES, JR., Examiner.

1. THE METHOD OF MANUFACTURING A RECIPROCAL FOURWAY SPOOL VALVE HAVING ARECIPROCAL CORE COMPRISING A PAIR OF ANNULAR LAND PORTIONS SPACED BY ANANNULAR REDUCED DIAMETER PORTION AND A HOUSING CO-OPERABLE THEREWITHCOMPRISING A PAIR OF ANNULAR PORTIONS OF LARGE INTERNAL DIAMETER SPACEDBY A FIRST ANNULAR PORTION OF REDUCED INTERNAL DIAMETER AND WHICH INTURN SPACED A SECOND PAIR OF REDUCED DIAMETER PORTIONS, WHICH CONSISTSOF FORMING EACH OF SAID PORTIONS AS A SEPARATE ANNULAR MEMBER ANDMACHINING SAID PAIR OF ANNULAR LAND PORTIONS AND SAID FIRST ANNULARPORTION OF REDUCED INTERNAL DIAMETER SIMULTANEOUSLY TO THE SAMETHICKNESS AND LIKEWISE MACHINING SAID PAIR OF ANNULAR PORTIONS OF LARGEINTERNAL DIAMETER AND THE ANNULAR REDUCED DIAMETER PORTION OF SAID CORESIMULTANEOUSLY TO A SECOND SAME THICKNESS AND ASSEMBLING SAID CORE ANDHOUSING TOGETHER WITH THE ANNULAR LANDS OF THE CORE IN FACE-TO-FACECORRELATION WITH THE HOUSING PORTIONS OF LARGE INTERNAL DIAMETER ANDWITH THE REDUCED DIAMETER PORTION OF THE CORE IN FACE-TO-FACE RELATIONWITH THE FIRST REDUCED INTERNAL DIAMETER PORTION OF THE HOUSING AND WITHTHE SECOND PAIR OF REDUCED DIAMETER PORTIONS POSITIONED ON AXIALLYOPPOSITE SIDES OF SAID ANNULAR PORTIONS OF LARGE INTERNAL DIAMETER.